1. Field of the Invention
The present invention relates to a semiconductor memory device and method of fabricating the same, and more particularly, to a semiconductor memory device and phase change memory device with a small heating area formed through a simple process, and a method of fabricating the same.
2. Description of Related Art
Along with the rapid development and advanced function requirements of portable products, nowadays a global market demand for memory is expanding rapidly, wherein the fast development of non-volatile memory is most remarkable. Accordingly, factories and research institutes are vigorously developing next generation memory device. Among various types of memory devices, phase change memory (PCM) device and Magnetoresistive RAM (MRAM) have drawn great interest.
Phase change memory is a non-volatile memory device comprising a phase change film whose resistance changes when the crystal phase of the phase change material changes under a thermal effect. The smaller area of the phase change film subjected to thermal effect through which the current passes, the smaller heating current is required for changing phase, and the smaller the RESET/SET driving current is. Correspondingly, a smaller drive transistor area is required, i.e. a smaller size memory unit cell. Therefore, various research are directed to the design of the size of heating area of the phase change film, for example, disclosed in EP 1339111 which was published in 2003.
However, at present, most known techniques relate to complicated method of etching contact holes in the dielectric layer or sacrificial layer for reducing heating area of the phase change film. When the contact holes are of a nanometer size, it would be difficult to reliably fill the hole and yield of the phase change film would be reduced significantly, and the dry pre-cleaning for the contact holes before film-coating becomes too complicated.